Calibration of GA1550 biotite standard for K/Ar and 40 Ar/ 39 Ar dating
Date
2011
Authors
McDougall, Ian
Wellman, Peter
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Volume Title
Publisher
Elsevier
Abstract
The mineral separate GA1550 biotite has become an international standard for K/Ar and 40Ar/39Ar dating studies, although it was prepared as an intralaboratory standard at ANU to monitor tracer depletion from a gas pipette. It is one of a small number of samples that has been calibrated against 38Ar tracers, some of which had been mixed with known amounts of atmospheric argon, so that a so-called primary calibration has been performed. By measuring GA1550 biotite against additional tracers from the same batch we have determined the radiogenic argon content of this sample as 1.342 (±0.007)×10-9mol/g, and together with the measured K content of 7.645 (±0.050) weight percent, we derive a best estimate for the K/Ar age as 98.5±0.5Ma, where the error is derived from averaging the ages determined relative to the 38Ar tracer.
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Keywords
Keywords: Atmospheric argon; Best estimates; Biotite standard; International standards; K/Ar geochronology; Mount Dromedary, Australia; Number of samples; Weight percent; Calibration; Geochronology; Mica; Standards; Argon; argon-argon dating; biotite; calibration; Biotite standard; Calibrations; K/Ar geochronology; Mount Dromedary, Australia
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Source
Chemical Geology
Type
Journal article
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2037-12-31